The present invention relates to a microwave oscillator and, more particularly, to a dielectric-controlled integrated oscillator which is furnished with a semiconductor active element chip and stabilized in oscillation frequency by a dielectric resonator.
In a dielectric-controlled integrated oscillator of the type described, it is a usual practice to mount a substrate made of a material having a high dielectric constant on a button wall inside a metal chassis of a housing, and a semiconductor active element chip and a dielectric resonator on the substrate, the active element chip and dielectric resonator being electromagnetically coupled to each other. The top of the housing is closed by a cover plate to complete a single oscillator package. Generally, the semiconductor active element chip in use has to be protected from the atmospheric air (particularly moisture) by hermetically seraling the oscillator package. Such is usually implemented by soldering or otherwise sealingly connecting the metal chassis to the cover plate after the installation of the substrate, active element chip and the like in the chassis.
The problem encountered with the above-described type of prior art oscillator is that when the oscillator in the sealed package has undergone a change in oscillation frequency due to aging, particularly temperature variation or the like, it is practically impossible to adjust the oscillation frequency. Additionally, it is difficult, if not possible, to set up a desired frequency while absorbing frequency deviation due to dimensional tolerance of the oscillator before the sealed confinement.
As discussed above, the prior art dielectric-controlled type integrated oscillator has failed to reconcile two major requirements to each other, i.e. hermetic or air-tight sealing and frequency adjustment.